Crown remover

ABSTRACT

A dental crown remover consisting of a U-shaped body having a pair of oppositely positioned piercing screws for engaging opposite sides of a crown and threaded pressure pin supported by the bottom of the U-shaped body for adjustably applying pressure through a pre-drilled hole in the crown to the tooth to which the crown is attached.

States Patet Wilson et a1.

Sept. 4, 1973 CROWN REMOVER Inventors: David J. Wilson, 207 N. Jefferson St., Athens, Ala. 35611; David J. Wilson, .lr., 1302-A Boxwood Dr., N.W., Huntsville, Ala. 35805 Filed: Dec. 27, 1971 Appl. No.: 212,486

US. Cl. 32/43 Int. Cl A61c 3/16 Field of Search 32/43 References Cited UNITED STATES PATENTS 5/1932 Flagstad et a1 32/43 Primary Examiner-Robert Peshock Attorney-C. A. Phillips [57] ABSTRACT A dental crown remover consisting of a U-shaped body having a pair of oppositely positioned piercing screws for engaging opposite sides of a crown and threaded pressure pin supported by the bottom of the U-shaped body for adjustably applying pressure through a predrilled hole in the crown to the tooth to which the crown is attached.

11 Claims, 11 Drawing Figures Patented Sept, 4, 1973 FIG. 4

FIG. 2

FIG. 5

FIG. H 6

. FIG. 7

FIG. 8

FIG. IO

cnown REMOVIER BACKGROUND OF THE INVENTION This invention relates generally to devices for removing crowns or restorations from teeth and particularly to an improved such device in which sides of a restoration are gripped and a force is applied through the crown to the surface of the tooth structure for removal of the crown.

GENERAL DESCRIPTION OF THE PRIOR ART Dental crowns have been used for many years for the restoration of decayed or otherwise broken teeth. Crowns are usually constructed of precious metals such as a gold alloy and the early ones were generally made of relatively thin wall material and were held in place by crimping the metal about the tooth near the gum line and cementation. Today crowns are cast of precious metal to precisely fit a pre-prepared tooth and are held in place by special cements which provide an extremely secure bond between the crown and tooth and thus removal has become more difficult. Removal, however, is often necessary in order to repair a bridge or treat a tooth. Various crown removers have appeared on the market and been described in patents, dating from the late l800s. The early crown removers were logically designed for the purpose of removing the relatively thin and not so firmly affixed crowns and typically such devices included arms which fit under the crimped edges. Once so positioned, a bolt supported by the device would be passed through a pre-drilled hole in the crown to the tooth and would be turned to apply sufficient pressure to remove the crown. Since present crowns do not have crimped edges and are attached much more securely, such devices can not be successfully applied today. Another approach and one sometimes used with modern crowns is to pre-drill a hole through a crown and then employ a self threading device to grip the crown in the predrilled hole, thereafter a screw is passed down through the center of the self threading screw to apply removal pressure. The difficulty with this approach is that in general the metal of the crown is too soft and too thin to support the self tapping thread and the thread is stripped by the attempted removal, thus preventing the removal of the crown. Because of the aforesaid and perhaps other difficulties the principal method of removing crowns today is to simply split the crown along a line by means of a high speed drill and then simply pry the crown away from the tooth structure. The difficulty here, is of course that this procedure substantially damages the crown, requiring either extensive repair or replacement by a new crown.

SUMMARY OF THE INVENTION Accordingly, it is the object of the present invention to provide a new and improved crown remover which enables crowns to be removed with slight damage and thus enabling them to be readily and inexpensively cemented back in place after the desired tooth repair has been accomplished.

The present invention contemplates a yoke or U- shaped body member having a fixed inner dimension width of 0.2 to 1.5 inches. Tooth gripping pins are threaded into opposite side walls of the body member and a pressure pin is threaded through the top of the body member. To use the crown remover, a hole just slightly larger than the diameter of the pressure pin is first drilled through the center region of a crown and the crown remover is placed over the tooth with the pressure pin aligned with this hole. The piercing pins are then screwed inward until they grip or pierce the sidewalls of the crown and thus provide a secure side supporting means. Thereafter, the pressure pin is screwed inward through the hole in the crown, applying pressure to the tooth and enabling the crown to be removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of one form of the invention in position for the removal of a crown.

FIG. 2 is a cross-sectional view along lines 2-2 of FIG. 11.

FIG. 3 is a fragmentary view of a detail of construction.

FIG. 4 is a bottom view of the detail of construction shown in FIG. 3.

FIG. 5 is a cross-sectional view of a portion of a mod ified form of the invention as would be seen by a view from the same aspect as FIG. 2.

FIG. 6 is a top view of the yoke portion of the device of FIG. 5 with the pressure application assembly re moved.

FIG. 7 is a fragmentary view of a portion of the pressure application assembly shown in FIG. 5.

FIG. 8 is an end view of the detail shown in FIG. 7.

FIG. 9 is a side view of still another form of the invention particularly adapted for the removal of crowns from front teeth.

FIG. 10 is a top view of the invention as shown in FIG. 9, omitting from the view the tooth and crown with which the invention is used.

FIG. 11 is a side view of an alternate form of screw construction to that illustrated in the other figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring initially to FIGS. 14, yoke 10 is constructed of to steel and is configured tp include an enlarged upper body region 12 and lower leg or side members 14 and 16, forming together a relatively wide U-shaped device. Like screws 18 and 20 are adapted to screw in and out of threaded regions 22 and 24 of side members 114 and 116. The ends 26 and 28 of screws 18 and 20, respectively, are pointed to pierce or grip the sidewalls of crown 30. Screw 32 threads into threaded region 33 of upper body region 12 and includes pin portion 34 of reduced cross-section which extends axially from the lower end of screw 32. The end of pin portion 34 is sufficiently flat to provide a blunt engaging surface to tooth 38 with which the crown remover is illustrated.

In operation, yoke 10 is positioned over a crown 30 and screws 18 and 20 tightened, at least slightly. Screw 32 is then turned down sufficiently to mark crown 30 for drilling a hole in crown 30 which is represented by hole 40 in FIG. 2. Screws l8 and 20 are next loosened, the crown remover removed and the hole drilled. After this, yoke M) is again placed over crown 30 and screws 18 and 20 reinserted in their previous positions and screws 18 and 20 tightened to the positions shown and thus crown 30 is firmly gripped by the crown remover. Screw 32 is then tightened moving pin 34 through crown 30 to the position shown wherein end 36 of pin 34 is in engagement with tooth 38. Next bolt 32 is further tightened to provide sufficient pressure between tooth 38 and crown 30 until cement binding the upper surface 42 of tooth 38 with the lower surface 44 of crown 30 is broken, enabling crown 30 to be removed.

With the crown removed, appropriate repairs or treatment are made to tooth 38 and crown 30 is again cemented to tooth 38. It is, of course, necessary prior to replacing crown 30 to repair the pierced and drilled surfaces and this is readily accomplished in view of the relatively small areas affected.

Another method of operation of the invention consists of following these steps: a hole is first drilled through the approximate center of crown 30 to the upper edge of tooth 38. The diameter of this hole is sufficiently large to accommodate pin 34. Screws 18 and 20 are backed off sufficiently to enable placement of the crown remover over crown 30 and the crown remover is then positioned over the crown with care being taken to guide pin 34 through pre-drilled hole 40 in crown 30. Thereafter, screws 18 and 20 are tightened to grip the crown securely. If desired, gripping may be assisted by pre-drilling the sides of the crown at points of contact between screws 18 and 20 and crown 30. Once crown 30 is securely gripped by screws 18 and 20, screw 32 is tightened to force pressure pin 34 against tooth 38, and crown 30 is broken away from the tooth.

FIGS. -8 depict an alternate embodiment of the invention which is particularly constructed to simplify alignment of pressure pin 34 in a pre-drilled hole in a crown. Yoke 50 includes an elongated slot 52 in which screw assembly 53 is adjustably mounted. Screw assembly 53 consists of sleeve 54 having outer 55 and inner 56 (position shown) threads and a mounting flange 57 at one end. A screw 32, identical to the same part as described above with respect to FIGS. 1-41, is threaded into the inner thread 56 of sleeve 54. Screw assembly 53 is secured to yoke 50 by means of nut 58 enabling bolt assembly 53 to be adjustably positioned within slot 52, nut 58 being loosened to enable adjustment and tightened to secure bolt assembly 53 in the desired position with respect to the point on a crown which is to be drilled. Once positioned in the desired position the side clamping screws 18 and 20, not shown in FIG. 5, are operated in the same fashion as described above with respect to FIGS. l-4 to remove a crown.

FIGS. 9 and show still another embodiment of the invention, one which is particularly adapted for the removal of crowns from front teeth. One significant difference of it over the other embodiments is that in place of screw there is provided two fixed mounted pin members 62 and 64 having sharpened ends 66 and 68 which are positioned to pierce a crown on each side of pin 34. Employment of this embodiment of the invention is as follows. Yoke 60 is positioned over crown 69 and screw 18 tightened sufficiently to enable drill holes to be marked in crown 69 for ends of pins 62 and 64. Yoke 60 is then removed and crown 69 drilled to accommodate piercing ends 66 and 68 of pins 62 and 64, respectively. Yoke 60 is then again placed over crown 69 and screw 18 is tightened. Screw 32 is also tightened sufficiently to mark a position for a hole to be drilled in crown 69 to accommodate pin 34 of bolt 32. Yoke 60 is then removed, the hole drilled and the yoke replaced. Finally, screw 18 is tightened to clamp the yoke in place and screw 32 is tightened to force pin 34 against tooth 70 until cement holding the crown and tooth together is broken, enabling the crown to be removed.

Pin 34 may be either integral with screw 32 to enable one piece construction or a dowel pin 34 may be mounted in the end of screw 32. The pointed ends 26 and 28 of screws 18 and 20 may be formed of a separate member or as an integral part of these screws. Pins 62 and 64 (FIGS. 9 and 10) may be replaced with pointed screws. Alternately the engaging ends of screws 18 and 20 and pins 62 and 64 may be replaced with a soft surface material such as nylon, silver, etc. to prevent marring of cosmetic crown surfaces of porcelain or plastic.

Screws 18, 20 and 22 should be no larger than inches in diameter. The ratio of the thicknesses of the legs or sides of a yoke to the overall length of the yoke should be between 1:2 and 1:20. The ratio of the length of the legs or leg portions of the yoke to the overall length of the yoke should be between 1:0.2 and 1:10. The slot in the yoke of FIG. 6 should have a length no more than five times its width. All components are constructed of high strength material such as strainless steel with the exception of the screws which may be dipped or plated or fitted with a softer material to prevent scarring of porcelain or plastic crowns.

FIG. ll illustrates an Allen screw 72 which would replace a screw 18 or 20 and includes a broad tip 74 of silver, lead or plastic. Typically the tip should have a hardness characterized by Brinell numbers less than 70 and preferably between 50 and 5. In the Rockwell scale the hardness figures would be for a comparable hardness range. Thus the tip in this illustration is of softer material than a yoke or the balance of screw 72 which are of steel. Where used they would not puncture the crown and gripping of the crown would be by lateral gripping pressure.

What is claimed is:

l. A dental crown remover comprising:

a yoke having fixed spaced leg portions adapted to extend longitudinally parallel with the length dimension of a tooth interconnected at one end by a main body portion adapted to fit over the end of a tooth;

clamping means comprising a screw adapted to be received by a threaded opening in one of said leg portions of said yoke for applying a linear pressure between said leg portions and sides of a crown mounted on a tooth;

pressure application means supported by said main body portion of said yoke and including an end portion adapted to pass through 'a pre-drilled hole in a dental crown and adjustably apply pressure between said main body portion and a tooth to which the crown is affixed in a direction normal to the said linear pressure applied by said clamping means to a said crown; whereby upon applying said pressure, said crown is forced apart from said tooth.

2. A crown remover as set forth in claim 1 wherein said screw of said clamping means includes a pointed end region adapted to pierce the surface of a dental crown.

3. A crown remover as set forth in claim 1 wherein said clamping means comprises gripping means mounted on the opposite said leg portion for applying lateral pressure between said last named leg portions of said yoke and a crown.

4. A crown remover as set forth in claim 3 wherein said gripping means comprises a pair of screws and both said leg portions of said yoke include threaded openings for receiving said screws.

5. A crown remover as set forth in claim 1 wherein said clamping means comprises a pair of fixed spaced pins supported by the opposite said leg portion of said yoke.

6. A crown remover as set forth in claim 1 wherein:

said main body portion of said yoke includes an elongated slot, the longitudinal axis of which extends normal to the direction of said leg portions of said yoke, and

further comprises adjustable mounting means for supporting said pressure application means in said slot;

whereby said pressure application means may be be adjustably positioned with respect to the legs of said yoke for positioning said end portion at a desired lateral position with respect to a crown to be removed.

7. A crown remover as set forth in claim 6 wherein said adjustable screw mounting means includes a slot in said main body portion of said yoke for adjustably supporting said pressure application means and the length of said slot, extending in the direction between legs, is between L5 and 5 times the width of said slot.

h. A crown remover as set forth in claim 1 wherein the ratio of the lengths of said leg portions of said yoke to the overall length of said yoke is within the range of 1:02 and 1:10. Y

9. A crown remover as set forth in claim 8 wherein the ratio of the thicknesses of said leg portions to the overall length of said main body portion of said yoke is between 1:2 and 1:20.

10. A crown remover as set forth in claim 1 wherein said clamping means includes end regions adapted to contact a said crown and which are characterized by Brinell numbers less than 70.

111. A crown remover as set forth in claim 1 wherein said pressure application means supported by said main body member comprises a screw and said main body member includes a threaded opening for receiving said 

1. A dental crown remover comprising: a yoke having fixed spaced leg portions adapted to extend longitudinally parallel with the length dimension of a tooth interconnected at one end by a main body portion adapted to fit over the end of a tooth; clamping means comprising a screw adapted to be received by a threaded opening in one of said leg portions of said yoke for applying a linear pressure between said leg portions and sides of a crown mounted on a tooth; pressure application means supported by said main body portion of said yoke and including an end portion adapted to pass through a pre-drilled hole in a dental crown and adjustably apply pressure between said main body portion and a tooth to which the crown is affixed in a direction normal to the said linear pressure applied by said clamping means to a said crown; whereby upon applying said pressure, said crown is forced apart from said tooth.
 2. A crown remover as set forth in claim 1 wherein said screw of said clamping means includes a pointed end region adapted to pierce the surface of a dental crown.
 3. A crown remover as set forth in claim 1 wherein said clamping means comprises gripping means mounted on the opposite said leg portion for applying lateral pressure between said last named leg portions of said yoke and a crown.
 4. A crown remover as set forth in claim 3 wherein said gripping means comprises a pair of screws and both said leg portions of said yoke include threaded openings for receiving said screws.
 5. A crown remover as set forth in claim 1 wherein said clamping means comprises a pair of fixed spaced pins supported by the opposite said leg portion of said yoke.
 6. A crown remover as set forth in claim 1 wherein: said main body portion of said yoke includes an elongated slot, the longitudinal axis of which extends normal to the direction of said leg portions of said yoke, and further comprises adjustable mounting means for supporting said pressure application means in said slot; whereby said pressure application means may be be adjustably positioned with respect to the legs of said yoke for positioning said end portion at a desired lateral position with respect to a crown to be removed.
 7. A crown remover as set forth in claim 6 wherein said adjustable screw mounting means includes a slot in said main body portion of said yoke for adjustably supporting said pressure application means and the length of said slot, extending in the direction between legs, is between 1.5 and 5 times the width of said slot.
 8. A crown remover as set forth in claim 1 wherein the ratio of the lengths of said leg portions of said yoke to the overall length of said yoke is within the range of 1:0.2 and 1:10.
 9. A crown remover as set forth in claim 8 wherein the ratio of the thicknesses of said leg portions to the overall length of said main body portion of said yoke is between 1:2 and 1:20.
 10. A crown remover as set forth in claim 1 wherein said clamping means includes end regions adapted to contact a said crown and which are characterized by Brinell numbers less than
 70. 11. A crown remover as set forth in claim 1 wherein said pressure application means supported by said main body member comprises a screw and said main body member includes a threaded opening for receiving said screw. 